This protocol allows us to capture longitudinal information from HIV seropositive subjects providing an active surveillance system for the identification of HIV-associated cognitive impairment and dementia among patients from the Multicenter AIDS Cohort Study (MACS), and the Johns Hopkins Moore Clinic (for patients with HIV infection). In publications this year, in the MACS, we showed that sustained decline in neuropsychological performance, as measured by an abbreviated neuropsychological battery consisting of the Trailmaking and Symbol Digit tests, was a powerful predictor not only for dementia, but also for progression to AIDS and survival. Individuals with sustained neuropsychological decline were 5 times more likely to progress to frank dementia (Sacktor, 1996). In a study comparing neuropsychological performance between injecting drug uers and homosexual men, Concha et al (1997) found that risk behavior for HIV acquisition was not an independent predictor of neuropsychological performance. Finally, analysis or neuropsychological performance over several years of follow-up in a cohort of injection drug users showed similar results to our previous findings among homosexual/bisexual men, namely that neuropsychological performance does not deteriorate during the prolonged medically asymptomatic phase of HIV infection (Selnes 1997).